Blackened/ bruised combs??

[Momoftres]

A few of my hens have this blackish discoloration on their combs. I just noticed it a couple of days ago. They are about a year and a half.
There are no scabs or lesions just discoloration. Is this normal?

 

[Wyorp Rock]

Looks like a bit of dried blood and dirt to me.
It will wear off, but if you feel you need to, you can take a damp cloth and wipe them off.